1. Technical Field
The present invention relates to a fiber component having a splice section used for fiber laser device and laser device employing the fiber component. In particular, it relates to heat dissipation of a fiber component.
2. Background Art
Recently, laser has been used for welding from the reasons of providing less deformation and high welding speed, and also used for cutting from the reasons of providing high cutting speed and a well-finished cutting surface. Of solid-state laser capable of light guiding with optical fiber, fiber laser has rapidly become popular because of its high-power output and high quality of laser beams.
The fiber laser is mostly made of thin optical fibers with a diameter of 1 mm or less, and through which, high-power laser light travels. Due to the structure above, for example, light generated by mode conversion at a fusion splice section between optical fibers can heat the optical fiber and burn it out. As fiber laser device has increase in output, the heat generation and burn-out of optical fibers has been a big problem to be worked out.
FIG. 10A through FIG. 10D show the main structure of an ordinary optical fiber having a silica core and used for laser device. Specifically, each of FIG. 10A and FIG. 10B is a cross-sectional view, taken along a direction of light propagation, of an ordinary optical fiber having a silica core; whereas each of FIG. 10C and FIG. 10D is a cross-sectional view, taken along a direction perpendicular to light propagation, of an ordinary optical fiber having a silica core.
In FIG. 10A and FIG. 10C, core 201—through which laser light travels—is mainly made of silica and is surrounded by a resin layer. The resin layer has inner resin coat 203 and outer resin coat 204.
Core 201 shown in FIG. 10B and FIG. 10D is made of silica or silica in which an excitable medium or germanium is doped. Core 201 is surrounded by clad 202 made of silica or fluorine-doped silica. Core 201 and clad 202 have difference in refractive index. Clad 202 is surrounded by a resin layer of inner resin coat 203 and outer resin coat 204.
Other than the structures described above, there is an optical fiber having silica-based sections formed in three layers or more, but such a structure is not shown here.
Hereinafter, the structure shown in FIG. 10A and FIG. 10C is described as an example of the optical fiber. Each of FIG. 11A, FIG. 11B, and FIG. 11C is a cross-sectional view showing the structure of an ordinary optical fiber and its profile of refractive index.
The resin layers as a coat on the core, as shown in the examples of FIG. 11A through FIG. 11C, have different patterns, and the pattern depends on difference in refractive index of inner resin coat 203 and outer resin coat 204. Further, there is an optical fiber having resin coat of three-or-more layers, but such a structure is not shown here. The left part of FIG. 11A through FIG. 11C shows the profile of refractive index of each example. The refractive index increases toward the left side of the double-headed arrow.
Each of FIG. 12A, FIG. 12B, and FIG. 12C is a cross-sectional view of the structure of a conventional fiber component, showing an example of fusion splicing of a conventional optical fiber.
FIG. 12A shows fusion splice section 206 connecting a single optical fiber with another single optical fiber. An ordinary process of fusion splicing is as follows: prior to fusion splicing, the resin coat on core 201 is removed and the exposed core is cut off into a predetermined length. After that, core 201 of each optical fiber is fused and connected with each other (see Japanese Unexamined Patent Application Publication No. H01-191807, for example). Therefore, after fusion splicing, the part adjacent to fusion splice section 206 has no resin coat.
However, fusion splice section 206 with no resin coat can decrease the strength of the structure. From the reason, it is often recoated with resin, as shown in FIG. 12B. The part adjacent to fusion splice section 206—from which the resin coat has been removed for fusion splicing—is coated again with recoating resin 207 after fusion splicing (see Japanese Unexamined Patent Application Publication No. 2009-115918, for example).
To suppress heat generated by light leaked from fusion splice section 206 and the periphery of it, the structure shown in FIG. 12C has heatsink 208. Heatsink 208 converts the leaked light into heat and dissipates it to the outside. Fusion splice section 206 is covered with heatsink 208 and fixed in groove 209. Further, fusion splice section 206 is recoated with recoating resin 207 of a resin material that transmits the light leaked from fusion splice section 206 (see Japanese Unexamined Patent Application Publication No. 2007-271786, for example.).
According to the prior-art measures against heat generation described above, fusion splice section 206 has to be coated with recoating resin.
In some fiber components, however, resin recoating can cause burn-out due to considerable leakage of light from fusion splice section 206 of the optical fiber, and therefore, recoating process cannot be employed for such a component.
When light fails to escape from the resin recoating section, the light can leak into a resin coat and generates heat in the resin coat. This can cause burn-out of an optical fiber.